This cool little guy does more than just measuring temperature with a 0.5 degree resolution and reporting it via I2C - it is also a complete thermostat with user-settable trigger and hysteresis. The polarity of the digital output can be inverted - so that the output goes high or low, depending on your needs, when it reaches the alarm. The output supplies up to 10mA, enough to drive a beefy MOSFET or even a solid state relay.